intersection interval dates between two tables

Question

Hello I need to intersect two tables with interval dates

Timeline 1

start               | end
---------------------------------------------
2016-12-19 08:00:00 | 2016-12-19 08:30:00
2016-12-19 09:30:00 | 2016-12-19 11:00:00

Timeline 2

start               | end
---------------------------------------------
2016-12-19 08:30:00 | 2016-12-19 10:00:00
2016-12-19 10:30:00 | 2016-12-19 11:00:00

here's SQL i tried:

SELECT * FROM start, end FROM timeline1 
INTERSECT
SELECT * FROM start, end FROM timeline2 

need result like this:

Total: 00:60:00

Answer 1

Use range operators * and &&:

select tsrange(t1."start", t1."end") * tsrange(t2."start", t2."end") as "intersections"
from timeline1 t1
join timeline2 t2 
on tsrange(t1."start", t1."end") && tsrange(t2."start", t2."end");

                 intersections                  
-----------------------------------------------
 ["2016-12-19 09:30:00","2016-12-19 10:00:00")
 ["2016-12-19 10:30:00","2016-12-19 11:00:00")
(2 rows)    

Sum of intervals:

select sum(upper("intersections")- lower("intersections")) as total
from (
    select tsrange(t1."start", t1."end") * tsrange(t2."start", t2."end") as "intersections"
    from timeline1 t1
    join timeline2 t2 
    on tsrange(t1."start", t1."end") && tsrange(t2."start", t2."end")
) s

  total   
----------
 01:00:00
(1 row)